This invention relates to a mechanism which can be combined with a lever to generate an output force greater than that on the drive side, and more particularly to a mechanism that provides such a force output after the drive member is driven forward and its forward resistance is increased during its stroke.
The lever is the most common mechanism used to obtain force amplification in order to generate an output force greater than the input force of the drive part. For example, it is used in driving the brake shoe in a railroad car brake system. (See Utility Model Kokai No. 59-132467.)
When the input force is increased by a lever mechanism, the amount of displacement at the power (or input) point naturally becomes greater than the amount of displacement at the action (or output) point by the lever ratio. However, in driving a brake shoe, it is only after the brake shoe engages the wheel that the large output force is required. The force required during the time the brake shoe is separated from the wheel until it contacts the wheel, can be simply the amount necessary to move it, and it is not necessary to generate a higher force by means of a lever during this time. However, in known brake systems, as in Utility Model Kokai No. 59-132467, for example, the output rod of the pneumatic cylinder is connected to the power point of the force lever and the action point is fitted to the brake push rod. Since the brake shoe is separated from the wheel when the brake is not working, it is driven such that a large output force is generated by the lever even during the time prior to the brake shoe touching the wheel. In the brake system, the necessary stroke of the push rod is not so large, but the driving stroke becomes quite large because of the above-mentioned lever ratio. Therefore it is difficult to obtain compact packaging because the movement until the brake shoe touches the wheel is done through a force amplifying lever.
In addition, in general, very often a certain amount of stroke is necessary until the pressing parts contacts the object, although the pressing stroke is not so large if the pressing part is strongly pressed against the objective item. For example, in a press, very often the workability is better when the space between the upper metal mold and lower metal mold is relatively large.